The present invention relates to an apparatus for testing a device with a high frequency signal and, more particularly, to an apparatus for testing a device by delivering a high frequency signal with a coaxial cable at or near the device.
Automatic test equipment systems or ATE systems are used to test devices such as semiconductor devices. An ATE system typically comprises a tester that generates test signals which are transmitted to a test head. The test head houses a plurality of modules. The test signals are transmitted from the modules to contact pins or pogo pins. The pins are arranged to contact the periphery of a circuit board or loadboard. Traces in the loadboard deliver the test signals from the periphery of the loadboard to a socket at the center of the loadboard. A device under test or DUT is inserted into the socket to establish electrical contact for testing. Thus, the test signals are transmitted from the tester to the DUT through the modules, contact pins, loadboard and socket. The resulting signals from the DUT are received by the tester for evaluation through the same elements.
The semiconductor devices are typically tested with low frequency signals. With the development of new types of semiconductor devices along with new testing protocols, it is currently preferable to test a DUT with a higher frequency signal.
The use of higher frequency signals has revealed certain disadvantages with the conventional ATE system. In the conventional ATE system, the loadboard can be very large and traces from the periphery of the loadboard to its center can reach 12 inches in length or even longer. Such long traces present certain problems with higher frequency test signals. First, parasitic loss in the trace is proportional to the frequency of the test signal in the trace. A high frequency signal at one of end of the a long trace can be lost by the time the signal reaches the other end of the trace. Second, even if the signal is not completely lost, the parasitic loss can create a phase difference in the signal that is not desirable. Third, the close proximity of long traces with high frequency signals can result in milli-volt fluctuations due to arc potential. Such fluctuations can destroy the high frequency signal.